U.S. Pat. No. 4,070,526 to J. Pfenning et al., discloses radiation-curable diorganopolysiloxane molding compositions which contain
(A) a mercaptoalkyl-containing diorganopolysiloxane PA1 (B) a vinyl-containing organopolysiloxane PA1 (C) a vinyl monomer and PA1 (D) a photosensitizer. PA1 (A) at least one mercaptoalkyl-containing compound which contains at least two SiC-bonded radicals per molecule of the general formula EQU HS--R.sup.2 -- (I) PA1 where R.sup.2 represents a divalent hydrocarbon radical having from 1 to 8 carbon atom(s) per radical, selected from the group consisting of mercaptoalkyl-containing organopolysiloxanes and cocondensates of mercaptoalkyl-containing organosilicon compounds containing groups capable of condensation, and hydroxyl-containing organic compounds, PA1 (B) at least one vinyl-containing compound which is compatible with constituent (A) and contains at least two groups per molecule of the general formula EQU R.sup.4 CH.dbd.CR.sup.3 C(O)O-- (II) PA1 where R.sup.3 represents a hydrogen atom or a methyl radical, and R.sup.4 represents a hydrogen atom or an alkyl radical having from 1 to 3 carbon atom(s) per radical, and PA1 (C) a mixture of a strong organic base selected from the group consisting of quaternary ammonium hydroxides, quaternary ammonium alkoxides, and tertiary, secondary and primary amines, and a weak protonic acid.
These compositions are preferably crosslinked by irradiation with ultra-violet light. The compositions are used in the production of adhesive-repellent coatings.
It is an object of the present invention to provide compositions which contain a mercaptoalkyl-containing compound selected from the group consisting of mercaptoalkyl-containing organopolysiloxanes and cocondensates of mercaptoalkyl-containing organosilicon compounds having groups capable of condensation, and hydroxyl-containing organic compounds as crosslinking agents for vinyl-containing compounds. Another object of the present invention is to provide compositions containing mercaptoalkyl-containing organopolysiloxanes as crosslinking agents for vinyl-containing compounds which can be cured at elevated temperatures. Still another object of the present invention is to provide compositions containing mercaptoalkyl-containing organopolysiloxanes as crosslinking agents for vinyl-containing compounds which contain a catalyst system having a long shelf life and are suitable for the production of coatings. A further object of the present invention is to provide compositions containing mercaptoalkyl-containing organopolysiloxanes as crosslinking agents for vinyl containing compounds which give paints that are hard, have strong adhesion to the substrate on which they are applied, have good gasoline resistance and cure well in deep section layers.